1. Field of the Invention
The field of the invention is data processing, or, more specifically, methods, apparatus, and products for controlling an operational mode for a logical partition on a computing system.
2. Description of Related Art
The development of the EDVAC computer system of 1948 is often cited as the beginning of the computer era. Since that time, computer systems have evolved into extremely complicated devices. Today's computers are much more sophisticated than early systems such as the EDVAC. Computer systems typically include a combination of hardware and software components, application programs, operating systems, processors, buses, memory, input/output devices, and so on. As advances in semiconductor processing and computer architecture push the performance of the computer higher and higher, more sophisticated computer software has evolved to take advantage of the higher performance of the hardware, resulting in computer systems today that are much more powerful than just a few years ago.
One area in which computer software has evolved to take advantage of high performance hardware is a software tool referred to as a ‘hypervisor.’ A hypervisor is a layer of system software that runs on the computer hardware beneath the operating system layer to allows multiple operating systems to run on a host computer at the same time. Hypervisors were originally developed in the early 1970's, when company cost reductions were forcing multiple scattered departmental computers to be consolidated into a single, larger computer—the mainframe—that would serve multiple departments. By running multiple operating systems simultaneously, the hypervisor brought a measure of robustness and stability to the system. Even if one operating system crashed, the others would continue working without interruption. Indeed, this even allowed beta or experimental versions of the operating system to be deployed and debugged without jeopardizing the stable main production system and without requiring costly second and third systems for developers to work on.
A hypervisor allows multiple operating systems to run on a host computer at the same time by providing each operating system with its own set of computer resources. These computer resources are typically virtualized counterparts to the physical resources of a computing system. A hypervisor allocates these resources to each operating system using logical partitions. A logical partition is a set of data structures and services that enables distribution of computer resources within a single computer to make the computer function as if it were two or more independent computers. Using a logical partition, therefore, a hypervisor provides a layer of abstraction between a computer hardware layer of a computing system and an operating system layer.
Although a hypervisor provides added flexibility in utilizing computer hardware, utilizing a hypervisor does have drawbacks. When a hypervisor provides resources to an operating system through a logical partition, the resources provided through the logical partition may not match the resources required by the operating system. For example, a hypervisor may attempt to provide processing resources according to a particular version of a processor architecture, when the operating system only supports older versions of the processor architecture. Examples of processor architecture versions may include IBM's POWER5™, which is an implementation of version 2.02 of the PowerPC™ processor architecture, and IBM's POWER4™, which is an implementation of version 2.01 of the PowerPC™ processor architecture. Moreover, when a hypervisor migrates a logical partition from one computing system to a target computing system, the computer resources provided by a hypervisor in the target computing system may not match the resources required by the operating system running in the partition. A mismatch between the resources provided by a hypervisor and the resources required by an operating system typically results in partition failure. As such, readers will appreciate that room for improvement exists for controlling an operational mode for a logical partition on a computing system.